The present invention relates to a means for immobilizing a contact lens to facilitate measurement of its physical dimensions.
The use of contact lenses to compensate for refractive error and thereby improve visual acuity is based on the shape of the lens and its relationship to the eye of the wearer. In order to provide the proper fit to the eye of the wearer, the concave surface of the lens must be of the proper curvature. The shape and physical dimensions of the lens also determine the optical characteristics of the lens, which interact with the eye of the wearer, to produce the desired degree of compensation. Numerous means exist for determining the physical dimensions of the eye of the wearer in order to specify the physical dimensions of the lens to be used by the particular wearer. In addition, devices exist for the measurement of the physical dimensions of a contact lens to ensure that it fits the wearer and produces the desired degree of compensation.
A particular problem exists for the measurement of the physical dimensions of what are termed "soft" or "hydrophilic" contact lenses because the lens is soft, supple and readily deformable. As a result, physical forces applied to the lens have the potential to distort the lens and in turn disturb the measurements being taken.
References disclosing various techniques for measuring the physical characteristics of soft contact lenses include radius gauge type apparatus, as for example, that show in U.S. Pat. No. 4,072,428. U.S. Pat. No. 3,779,648 discloses a means for holding a contact lens in order to effect measurements thereon. U.S. Pat. No. 3,985,445 discloses an apparatus for measuring characteristics of contact lenses including a holder that is immersed in a liquid. The lens is placed within a collar-like member having an aperture appropriate to the diameter of the lens. In such a device not only is the lens contacted physically but the device requires the use of different collar-like members, the sizes of which are determined by the diameter of the lens being measured. Furthermore, such a device has a specialized function and is relatively complex and expensive. This type of device woud find use only by those who could justify a large capital investment.
In addition, there are numerous journal articles dealing with the measurement of contact lenses and specifically hydrophilic contact lenses that show means for supporting the lens within a fluid medium. All of the means known to support a contact lens to facilitate measurement of its physical or optical parameters involve the use of physical contact with the lens by a rigid member to support or immobilize the lens during measurement. Because of the physical contact with the lens all of such devices have the capacity to distort the lens. In addition, the portion of the device that contacts the lens must be able to accommodate lenses of various radii and diameters. Furthermore, many of the devices use special types of equipment rather than allow the use of standard optical measuring equipment in combination with a lens holding device.
It is the primary object of the present invention to provide a means for immobilizing a contact lens to facilitate measurement thereof without significant distortion.
It is a further object of the present invention to provide a means of immobilizing a soft or hydrophilic contact lens on the surface of a liquid medium such that its physical characteristics can be measured by the use of standard optical equipment.
Further objects of the present invention will be disclosed in connection with the description of the preferred embodiments set out below.